H36 



Issued January 17, 1908. 

U. S. DEPARTMENT OF AGRICULTURE. 

OFFICE OF EXPERIMENT STATIONS— BULLETIN 195. 

A. C. TRUE, Director. 



SIMPLE EXERCISES ILLUSTRATING SOME 

APPLICATIONS OF CHEMISTRY 

TO AGRICULTURE. 



BY 
K. L. HATCH, 

Principal of the Winyiebago County School of Agriculture and 
Domestic Economy, Wimieconne, Wis. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1908. 



.iograph 




Class ___SiiI^in 



1042 



Issued January 17. 1908. 



U. S. DEPARTMENT OF AGRICULTURE. 

OFFICE OF EXPERIMENT STATIONS— BULLETIN 195. 



7 



A. C. TRUE, Director. 



SIMPLE EXERCISES ILLUSTRATING SOME 

APPLICATIONS OF CHEMISTRY 

TO AGRICULTURE. 



BY 
K. L. HATCH, 

Principal of the Winnebago County School of Agriculture and 
Domestic Economij, Winneconne, Wis. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 



1908, 



V 



'xX-^' 



THE OFFICE OF EXPERIMENT STATIONS. 

A. C, True, Ph. I)., Sc D., Dinchn: 

E. W. Allen, I'h. I)., Af<sistani Director and Editor of Lld-pcriinciit )S7«/joh 

Record. 
W. H. Real, A. B., M. E., Chief of Editorial Division. 
Dick J. Crosby, M. S., Expert in A(jricullural Education. 

[Bull. 195.] 

(2) 



IS V^S<] 



LEITER OF TRANSMIITAL 



U. S. Department of Agriculture, 

Office of Experiment Stations, 
Washington^ D. 6'., Noaemher 20, 1007. 
Sir: I have the honor to transmit herewith, and to recommend for 
publication as Bulletin 195 of this Office, a series of exercises showing 
how rural school teachers can make simple and inexpensive demon- 
strations illustrating- some of the applications of chemistry to agri- 
culture. The bulletin is intended to supplement Bulletin 186 of this 
Office, Exercises in Elementary Agriculture, and was prepared under 
the direction of Mr. Dick J. Crosby, of this Office, by Mi\ K. L. 
Hatch, principal of the Winnebago County School of Agriculture and 
Domestic Economy, Winneconne, Wis. 

Respectfully, A. C. True, Director. 

Hon. James Wilson, 

Secretary of Agriculture. 

[BuU. 195.] 

(3) 



CONTENTS. 



Introduction 7 

Purpose of the bulletin 7 

Scope of the bulletin S 

Necessary material : S 

Part 1.— The plant 10 

Plant foods 10 

Exercise 1. To prepare carbonic-acid gas 11 

Exercise 2. To prepare limewater 11 

Exercise 3. To test for carbonic-acid gas 11 

Exercise 4. To illustrate carbon 12 

Exercise 5. To prepare oxj^gen 12 

Exercise G. To test for oxygen . 12 

Exercise 7. To prepare nitrogen 13 

Exercise 8. To test for nitrogen 13 

Exercise 9. To prepax'e hydrogen 14 

Exercise 10. To test for hydrogen 14 

Exercise 11. To prepare potash 15 

Exercise 12. To prepare phosphoric acid 15 

Exercise 13. To test stone for lime 15 

Exercise 14. To prepare lime 15 

Exercise 15. To make a collection of jihint foods 10 

Plant products 10 

Exercise 10. To test for starch 17 

Exercise 17. To test for sugar i_ 17 

Exercise IS. To test for oil IS 

Exercise 10. To test for protein 18 

Exercise 20. To illustrate plant fiber 18 

Part 2.— The soil 10 

Exercise 21. To illustrate plant foods which must be derived 

from the soil 20 

Exercise 22. To illustrate acids 20 

Exercise 23. To illustrate alkalis 20 

Exercise 24. To test for acids and alkalis 20 

Exercise 25. To test acidity and alkalinity of soils 21 

Exercise 20. To show that lime will " sweeten" a sour soil__ 21 
Exercise 27. To show that wood ashes will " sweeten "' a 

sour soil 21 

Exercise 28. To show that irrigation with underdrainage will 

remove alkali from the soil 22 

[Bull. 195] 

(5) 



ILLUSTRATIONS, 



Page. 

Fig. 1. Chemicals needed for the exercises in this bulletin !» 

2. Apparatus used in preparing oxygen !) 

3. Apparatus used in preparing nitrogen lo 

4. Apparatus used in preparing hydrogen 14 

5. A collection of plant foods 1(1 

[Bull. 195] 

(6) 



SIMPLE EXERCISES ILLUSTRATING SOME APPLICATIONS OF 
CHEMISTRY TO AGRICULTURE. 



INTRODUCTION. 

Many people have come to tliink of chemistry as a laboratory 
science, the workings of which are shrouded in mystery, and of chem- 
icals as liquids, powders, and crj^'stals confined in bottles and safely 
stowed away on the shelves of the apothecary shop. The science has 
been regarded too difficult for ordinary comprehension and the 
materials too illusive for our grasp. 

Such, however, is not the case. Chemistry is indeed a wonderful 
science, but its processes are taking place all around us and its com- 
pounds exist everj^where. The air we breathe is a mixture of chemi- 
cal elements and compounds, the water we drink is a chemical com- 
pound, the solid earth beneath us but a conglomerate mass of many 
chemicals. The plants which grow upon the surface of the earth are 
composed of only a few chemical substances, and the animals which 
feed upon the plants (and upon other animals) are but chemical com- 
pounds wrought in nature's laboratory by that mysterious process 
called life. 

PURPOSE OF THE BULLETIN. 

It is the purpose of this bulletin to aid the teacher in working out 
a series of simple exercises Avhich will acquaint the pupils with a few 
chemical elements of great importance in agriculture — those enter- 
ing into the structure of the plant and those composing plant-made 
compounds. 

The exercises are not intended for cliildren studying the science of 
chemistry or the science of agriculture, but for children unfamiliar 
with scientific methods and terms. For this reason the exercises are 
made very simple and the fewest possible technical terms are used. 
A\liere it has been necessary to choose between accurate technical lan- 
guage which might be a little confusing to the pupils and a less tech- 
nical statement expressed in language familiar to them, the latter has 
been chosen. The aim is simply to show the intimate relation between 
the plant, the air, and the soil, and to familiarize the farmers" chil- 
dren with a few chemical terms which must become household words 
if the principles underlying agriculture are to be taught successfully 
in the connnon schools. 

[Bull. 195] 

(7) 



SCOPE OF THE BULLETIN. 



The following topics are covered by the exercises outlined herein : 

(1) Those elements and compoinids, called plant foods, which are 
essential to the growth and development of the plant. 

(2) Those compounds, called plant products, which are formed by 
the plant out of the food which it consumes. 

(3) The three sources of plant food, viz, the soil, the air, and the 
water. 

(4) The meaning and the importance of the terms "Acids " and 
"Alkalis." 

(5) Methods of treating soils which are abnormally acid or alkali, 

NECESSARY MATERIALS. 

The necessary materials are of the simplest kind and can be pro- 
cured in any locality at very slight expense. The school children 
may be asked to provide the following items : 



1. Four or five old bottles. 

2. Two tin cans. 

3. A tin plate. 

4. A tin pan. 

5. Two tumblers. 

6. A glass fruit jar. 

7. Two or three feet of broom wire. 

8. A tbimble. 

0. Splinters of wood. 

10. Matches. 

11. Straws or woodbine or pipestems. 

12. Small pieces of waste zinc. 



l.S. A few pieces of charcoal. 

14. Two or three rusty nails. 

15. Two or three heavy white pie 

plates or sauce dishes. 

16. A tea spoonful of sulphur. 

17. A handful of fresh unslaked lime. 

18. A small bottle of vinegar. 

19. A handful of cotton. 

20. A small bottle of sulphuric acid 

from the creamery or cheese fac- 
tory. (The acid used in testing 
milk.)" 



To the above list must be added the following, which can 
purchased at any drug store (see fig. 1) : 

Alcohol (denatured) 6 $0.10 



be 



Potassium chlorate 

lodin 

Saltpeter 

Soda (saleratus) 

Ammonia 

Caustic potash 

Copper sulphate 

Cochineal or litmus paper 

Total 



0.5 
05 
,05 

,05 
, 05 
,05 
.05 
.05 



50 



" Great care must be exercised in working ivith sulphuric or other strong 
acids, as they arc strongly corrosive. They must not come in contact ivitli the 
flesh or clothes of the operator nor with ordinary metallic vessels and tnust be 
greatly diluted with water before being poured into the sink. 

^ Wood alcohol or ordinary alcohol may be used if denatured alcohol is not 
easily obtained. 
[Bull. 195] 



The teacher will need an alcohol lamp, which can be made from an 
ink bottle, as follows: Drive an empty cartridge shell through the 
cork, file off the closed end, and punch out the corJv inside the shell. 




Fig. 1. — Chemicals needed lor the exercises in tliis bulletin. 

Twist a string into a wick, draw it through the shell, and fill the 
bottle half full of alcohol (fig. 2). Evaporation of the alcohol may 
be prevented by covering the wick with a thimble. Either wood alco- 
hol, denatured alcohol, or 
kerosene ma}' be used, though 
the latter smokes badly and 
blackens the dishes heated by 
the flame. 

A lamp can also be made 
from a small tin box. Punch 
a hole through the cover from 
the under side, fill the box 
with cotton, and pull a wisp 
of it through the hole in the 
top for a wick. ]\Ioisten the 
cotton with two or three teaspoonfuls of alcohol, light, and you will 
have a lamp that will burn nicely for ten or fifteen minutes. 

The entire cost of the apparatus and supplies is a trifling outlay 
for any school. With this material at hand the earnest teacher will 
be able to work out the exercises outlined below in an interesting and 
an instructive manner. 

19595— OS— Bull. 195 2 




Fig. 2. — Apparatus used in preparing oxygen. 



10 

Part 1. — The Plant. 

plant foods. 

It is well known that a little plant is to be found in every perfect 
seed. When the seed germinates this plant lives principally on the 
food material stored in the seed until it develops roots and leaves. It 
is then iible to take in food from the air through its leaves, Avhile its 
roots absorb from the soil other food materials dissolved in water. 
Large quantities of this water are incorporated into the tissues of the 
plant, but by far the greater portion of it passes ofl' again into the 
air through the breathing pores of the leaves. Water, then, is im- 
portant to the plant for three reasons, viz : 

(1) It dissolves the plant foods in the soil. 

(2) It transports the plant foods upAvard from the roots toward 
the leaves. 

(3) It serves as a plant food itself. 

Out of its food materials the plant manufactures starch, sugar, 
oil, protein, fiber, and cellulose, compounds which go to make up the 
plant structure. Starch, sugar, oil, and protein are digestible and 
furnish food for men and animals. Fiber and cellulose are the indi- 
gestible parts of the plant. 

As has already been stated, there are three sources of plant food— 
the soil, the air, and the water. From the air the plant takes in 
oxygen and carbonic-acid gas through the breathing pores of the 
leaves. The leaves do not use the nitrogen of the air. This essen- 
tial and most expensive of plant foods is taken in l)y the roots of 
plants. Small quantities of nitrogen exist in soils in a form known 
as nitrates, which dissolve readily in water and enter the plant 
through its roots, in company with the other plant foods. The roots 
of leguminous plants, such as clovers, alfalfa, peas, and beans, are 
able also, Avith the aid of minute organisms known as bacteria, to 
use the uncombined niti'ogen in the soil air. 

Most of the plant foods are available in the soil in great abundance, 
but it is sometimes necessary to supply nitrogen (in the form of 
nitrates), phosphoric acid, and potash. These are called fertilizers 
and are the only plant foods which the plant ever has difficulty in 
getting. The other plant foods are lime, oxid of iron (iron rust), 
soda, magnesia, silica (largely sand), hydrochloric acid, and sul- 
phuric acid. Alumina and several other mineral compounds are fre- 
quently found in plants, luit are not considered essential to their 
perfect development. Lime is sometimes applied to the soil to 
" sweeten '' it or make it more friable, but not as a plant food. 

Allien the plant is burned the carbonic acid, water, oxygen, and 
nitrogen pass off again into the air. The mineral matter is left 

[Bull. 10.-.] 



11 

behind in the ash. When the chemist makes a complete analysis of 
a plant he first dries it at the temperatnre of boiling water. The loss 
in weight is water. He next burns the plant, " traps " the escaping 
gases, and weighs them. Finally he analyzes the remaining ash. In 
this way it is easy for him to learn just what substances are used by 
the plant in its growth. 

The first fifteen of the following exercises are intended to illustrate 
plant foods and simple tests for them. 

Exercise 1. — To Prepare Carbonic-acid Gas. 

Carbonic-acid gas is found in small quantities in the air. It is a 
product of the breathing of animals, the burning of wood and coal, 
and the decay of vegetation. 

To prepare it place a teaspoonful of soda in a glass half full of 
water and add to this a few teaspoonfuls of vinegar. Stir the mixture 
and gas will be given off in little bubbles. This is carbonic-acid gas, 
the same as that given off from the lungs, as will be shown by a later 
experiment. 

Exercise 2. — To Prepare Limewater. 

To test for carbonic-acid gas limewater may be used. It may be 
easily prepared as follows: 

Place a small handful of unslaked lime in a clean quart bottle, 
fill the bottle nearly full of water and allow it to stand for several 
hours, shake well and set aside until the undissolved lime settles and 
the water above it is perfectly clear. Pour off this clear liquid into 
another clean bottle. This clear liquid is limeAvater. Taste it to 
satisfy yourself. Cork the bottle tightly and set aside for testing 
carbonic-acid gas. If the bottle is kept corked the limewater will 
remain clear for a long time. AVlien the lime separates out the solu- 
tion should be thrown away and a fresh supply prepared. 

Exercise 3. — To Test for Carbonic-acid Gas. 

Make some carbonic-acid gas from vinegar and soda, as in Exercise 
1. Pour some of this gas into a glass containing a little limewater. 
The gas is heavier than air and can be poured from one vessel into 
another. Place your hand over the glass and shake it. The lime- 
w^ater becomes milky, due to the action of the carbonic-acid gas. 

Pour some freshly prepared limew^ater into a tumbler and blow 
bubbles through it with a straAV or j^ipestem. The limewater turns 
milky. This shows that carbonic-acid gas is given off by the lungs. 

Pour a little limewater into a bottle, place your hand over the 
mouth of the bottle, and shake it. If the air in the bottle is compara- 
tively free from carbonic-acid gas, the limewater will not be af- 

tBulI. 195] 



12 

fected. Set the bottle down and introduce into it a burning splinter. 
Leave it there until the flame goes out. Withdraw the splinter, place 
your hand again over the mouth of the bottle, and shake it. The 
limewater is now milky, show^ing that carbonic-acid gas is formed 
when wood burns. In the preceding test the presence of carbonic-acid 
gas in the air coming from the lungs is an evidence of combustion 
within the body. 

Place a little limewater in a saucer and set it on the floor of the 
schoolroom. In a little while it will become milky, showing the 
presence of carbonic-acid gas near the floor of our living rooms. 
Wliy not near the ceiling? 

Exercise 4.— To Illustrate Carbon. 

All kinds of coal are composed largely of carbon. Stove blacking 
is carbon. The " lead " in our pencils is carbon and not lead at all. 
"VVlien wood begins to burn it turns black, forming charconl. This 
charcoal is almost pure carbon. When any form of carbon burns 
carbonic-acid gas is formed. This gas is a compound of the hard, 
black, solid carbon and the oxygen of the air. 

Exercise 5. — To Prepare Oxygen, 

Double a piece of broom wire into a loop and twist it around a 
thimble. Push the free ends of the wire through a cork for a liandle 
(fig. 2). Fill the thimble half full of chlorate of potassium and hold 
it in the flame of the alcohol lamp. AVlien the chlorate melts oxygen 
will come off. It is a good plan to mix equal parts of clean, fine sand 
with the chlorate. This causes the oxygen to come off more rapidly. 
An empty brass cartridge shell can be used instead of the thimble. 

Exercise 6, — To Test for Oxygen, 

Wlien the chlorate of potassium in the above experiment becomes 
heated light a splinter in the blaze of the lamp and blow it out, leav- 
ing a bright red coal. Hold this glowing coal close over the thimble 
and it will burst into a brilliant flame. This is a test for oxygen. 
Oxygen is a very active element, and in a pure state it combines very 
readily with many other elements even at low temperatures. This 
combination is commonly called combustion. 

Bend a j)iece of fine wire into a loop, heat it, and dip this loop into 
some sulphur. Light the sulphur and hold it over the thimble, in 
wdiich the oxygen is being prepared, as before. The sulphur, and 
perhaps the wire, will burn with great brilliancy. 

[Bull. 195] 



13 



Exercise 7. — To I'repake Nitrockn. 



The air is composed of three gases — nitrogen, oxygen, and carbonic- 
acid gas. Four-fifths of it is nitrogen, nearly one-fifth is oxygen, and 
a very small part of it is carbonic-acid gas. If the oxygen and car- 
bonic-acid gas can be taken out of the air, nothing will then remain 
but the nitrogen. This may be accomplished by burn.ing out the 
oxyoen, i. e., converting it into carbonic-acid gas, and then dissolving 
the carbonic-acid gas in limewater in the following manner : 

Twist a piece of wire about a foot in length around a very small 
bit of cotton and bend it sharply about 3 inches from the end nearly, 
but not quite, double. Dip the cotton in alcohol, light the little torch, 
rest the loop with the torch standing up- 
right on the bottom of a dish containing 
some limeAvater. Now invert an empt}^ 
bottle over the torch and rest it on the bot- 
tom of the dish so that the neck will be 
immersed in the limewater (fig. 3). The 
oxygen will soon bui-n out of the bottle and 
water will rush in to take its place. The 
oxj'gen is now converted into carbonic-acid 
gas. Place your hand over the mouth of 
the bottle, still held beneath the water, 
invert it quickly, and shake. The lime- 
water immediately becomes milky, showing 
that the -carbonic-acid gas has been taken 
up by it. Practically everything except 
the nitrogen and the limewater have been 
taken out of the bottle. Set the bottle 
right side up on the table, remove your 

hand, and cover the bottle quickly with a piece of glass or a small 
board, and proceed immediately w^ith the following tests : 




Pig. 3. — Apparatus used in pre- 
paring nitrogen. 



Exercise 8. — To Test for Nitrogen. 



First note the color and odor of the gas. Light a long splinter 
and while still burning brightly thrust it into the bottle nearly to 
the limewater. It immediately goes out. This is a test for nitrogen. 
It is the exact opposite of oxygen. Like oxygen, it is colorless, odor- 
less, and invisible, but it will not burn and it will not support com- 
bustion. Thrust the burning sulphur into the bottle of nitrogen. 
The bottle must be kept covered as much as possible, as the oxygen 
of the air, being somewhat heavier than nitrogen, will soon get into 
the bottle and spoil the experiment. 

[Bull. 195] 



14 



Exercise 0. — To Prepare Hydrogen. 

Water is composed of two gases — hydrogen and oxygen. Oxygen 
has already been discussed. Hydrogen may be prepared by using 
some sulphuric acid and some waste zinc cut in small enough pieces 
to be put into a bottle. A scrap from an old stove board or the top 
of an old fruit can will answer. Place a small handful of the zinc 
pieces in an empty bottle and cover with w^ater (fig. 4). Xow add 
about one-fifth as much sulphuric acid as water used and hydrogen 
will come off rapidly in little bubbles. 

Precautions which must he ohscrved. — (1) Do not spill the acid on 
the floor, hands, or clothing. If by accident any should be spilled, it 

must be washed off immedi- 
ately with an abundance of 
water and, if possible, a 
little liquid ammonia ap- 
plied. 

(2) Do not hold the bot- 
tle in which the hydrogen is 
being prepared in the hands 
during the experiment. 

(3) Never pour water in- 
to the acid. Always pour 
the acid into the w^ater. 

(4) Always stand back 
when you light the hydro- 
gen. It sometimes explodes 
so violently as to break the 
bottle. 

(5) Evenwdien all of these 
precautions are observed the 
bottle may break, because it 

becomes so highly heated. Better set it in an earthen dish to catch 
contents, should it break. Never put acid in an ordinary metal dish. 
It will destroy most metals. 

Exercise 10. — To Test for Hydrogen. 

Light a match and hold it close over the mouth of the bottle in 
W'hich the hydrogen is being prepared. The hydrogen explodes with 
a puff and may take fire and burn wnth a nearh^ colorless flame at the 
mouth of the bottle. This is a test for hydrogen. Like oxygen and 
nitrogen, it is colorless, tasteless, and invisible. 

Should the gas take fire at the mouth of the bottle, hold a j^iece of 
cold glass over the flame. Little drops of water wnll sooji appear on 
the glass, showing that when hydrogen burns (i. e., unites with oxy- 

[Bull. 195] 




Fig. 4. — Apparatus used in preparing hydrogen. 



15 

gen under the influence of heat) water is formed. The observation 
shouhl be made before the flame has had time to heat the glass, other- 
wise there Avill be no condensation of moisture on the glass. 

Exercise 11.— To Prepare Potash. 

Potash is easily prepared from wood ashes. Pour 2 or 3 
quarts of water over a pan half filled with wood ashes and stir water 
and ashes together thoroughly. Set aside for a time and stir again. 
Repeat this several times, in order completely to dissolve the potash 
contained in the ashes. "When the ashes have finally settled, pour off 
the clear liquid on the top into another vessel, set it on the stove, and 
evaporate to dryness. The dry, white substance found on the bottom 
of this dish is potash. A little of it dissolved in water will make the 
water feel soapy. This " soapy feel " is a test for alkalis, to which 
group potash belongs. Repeat this exercise after Exercise 24 has 
been performed, and test the potash with litmus paper. 

Exercise 12. — To Prepare Phosphoric Acid. 

• Phosphoric acid, uncombined with other elements, is very difficult 
to obtain. P^or illustrative purposes, crude phosphoric acid may be 
easily jDrepared from bones by burning them to whiteness. Burned 
bone is practically a combination of phosphoric acid and lime. The 
lime may be removed by placing the burned bone, finely pulverized, 
in a bottle, covering it with water, and adding a small quantity of 
sulphuric acid. The lime Avill combine with the sulphuric acid and 
settle to the bottom and the clear liquid above it will contain the 
phosphoric acid. This is a very simple way to prepare it, and the 
liquid is sufficiently pure for illustrative purposes. 

Exercise 13. — To Test Stone for Lime. 

Break off a piece of stone as large as a hickory nut and pulverize it 
by pounding it with a hammer. Make a very fine powder, put the 
powder in a glass, cover it with water, and add a small quantity of 
sulphuric acid.° If the stone is a limestone, little bubbles of carbonic- 
acid gas will come off. Test it with limewater. If no gas comes off, 
the stone contains little or no lime. 

Exercise ]4. — To Prepare Lime. 

When a stone is known to contain lime it may be converted into the 
kind of lime used by builders by burning it in a stove for a day or two. 
When thoroughly burned take it out and make some limewater from 

" Observe the precautions noted on page 8 regarding the use of acids. 

[Bull. 195] 



16 

it as directed in Exercise 2. Test this limeAvater by tasting it and by 
blowing carbonic-acid gas throngh it from the hnigs. 

ExERCisK 15. — To Make a Collection of Plant Foods. 

It is a good plan to ilhistrate all plant foods by making a collection 
of them. Each substance should be placed in a separate bottle and 
properly labeled. Lime, oxid of iron (iron rust), soda, and silica 
(sand) are very easily obtained. Magnesia and ammonia can be pur- 
chased at any drug store. A few cents' worth of each will suffice. 
Vinegar is the commonest kind of acid. A small vial of this will serve 
to illustrate acid. Carbonic-acid gas has been studied and sulphuric 
acid is to be found with your supplies. The three essential fertili- 
zers — nitrogen, phosphoric acid, and potash — have already been pre- 




FiG. 5. — A collection of plant foods. 

pared. Saltpeter (potassium nitrate) is a good example of soluble 
nitrates (see fig. 5). 

Pupils should be encouraged to handle the plant foods until they 
become perfectlv familiar with them and can readily recognize each at 
sight. 

PLANT PRODUCTS. 

From 10 to 90 per cent of the entire weight of the plant is water and 
from 1 to 10 per cent is ash. These amounts vary so widely that it is 
hardly possible to find an average. In a very general way we may say 
that plants contain about 50 per cent of water and about 2 per cent of 

[Bull. 195] 



17 

ash. The remainder is composed of a variety of plant products, chief 
of which are starch, sugar, oil, protein, fiber, and cellulose. All of 
these except protein are composed of exactly the same elements — car- 
bon, oxygen, and hydrogen — combined in different proportions. 

Protein contains (in addition to hydrogen, oxygen, and carbon) 
nitrogen, sulphur, phosphoric acid, and sometimes other soil elements. 
It will be observed from their composition that none of t)ie plant 
products named, except protein, make any demands upon the soil. 
The plant gets its carbon from tlie carbonic-acid gas of the air and its 
hydrogen and oxygen from water. Out of these three elements it 
makes starch, sugar, oil, cellulose, and plant fiber. 

The difference between fiber and cellulose is very slight. By plant 
fiber we usually mean those threadlike tissues, like cotton and flax, 
which are easily separated from the plant in fibrous threads. Cellu- 
lose constitutes the essential part of the solid framework of the plant. 

If the i^lant be dried, pulverized, and boiled in water to which a 
little acid is added and then in water to which potash is added, the 
starch, sugar, oil, and protein will be dissolved out and only the indi- 
gestible fiber and cellulose will remain. 

By making use of the exercises which follow, the teacher may show 
that the products named above are to be found in plants. 

Exercise 1G. — To Test for Starch. 

Stir a pinch of starch into a little hot water. Dip a clean splinter 
into the iodin bottle, and a drop of this substance will adhere to the 
end of the splinter. Stir the starch water with the moistened splinter 
and it immediately turns blue. This is a test for starch. Iodin 
always turns starch blue, the intensity of the color varying with the 
amount of starch present. 

If seeds be pulverized and boiled in water the starch in them will be 
separated out. If the water in which the seeds have been boiled be 
treated with iodin in the way in which the starch water was treated, 
the presence of starch will be shown by the blue color. It is a good 
plan to use a white earthen dish for this experiment, as the white 
background makes it easy to see the slightest blue color. 

Another test for starch is made by dipping a cloth into the water 
in which the pulverized seeds have been boiled, afterwards drying 
and ironing it. The presence of starch is indicated by the increased 
stiffness of the cloth. 

Test potatoes, corn, beans, oats, and other seeds for starch. 

Exercise 17. — To Test for Sugar. 

There is no easy chemical test for sugar, though its presence in 
seeds and other parts of the plant is easily detected by the taste. The 
slightest sweet taste indicates the presence of sugar in some form. 

[Bull. 1051 



18 

Test rye, wheat, sweet corn, pumpkin seeds, and root crops for 
sugar. 

Exercise IS. — To Test fob Oil. 

If seeds containing oil be crushed on a j^iece of clean white paper, 
a grease spot will appear. Should this test fail to show oil, place the 
crushed seeds and paper on a tin plate in a moderately warm oven. 
Care must be taken not to scorch the paper. The high temperature 
will drive out the oil, and its presence will be indicated by a grease 
spot on the paper. 

Test nuts and small seeds for oil. 

Exercise V.). — To Test for Protein. 

The white of e^g is the best example of protein that can be easily 
obtained. The test for this compound is somewhat complicated, but 
if the directions here given are carefully followed there should be 
little difficulty in securing the characteristic reaction. Prepare first a, 
10 per cent solution of caustic potash by dissolving a stick of caustic 
potash (about i ounce) in a 2-ounce bottle of warm water. Care 
should be taken in handling caustic potash not to touch it to the fin- 
gers or clothes, as it is very strongly alkaline and will eat through the 
skin or the clothing. Secondly, dissolve a piece of copper sulphate 
(bluestone), about 4 inch in diameter, in a 2-ounce bottle of warm 
water. 

Pour a small quantity of white of egg on a white pie plate or 
sauce dish and cover it with a portion of the caustic potash solution. 
Warm the dish, but be careful not to cook the egg. Over this pour 
a little of the copper sulphate solution and stir with a clean si^linter. 
At first the only color perceptible will be the greenish-blue of the 
copper sulphate, but after ten or fifteen minutes a bright violet color 
will begin to appear and spread through the solution wherever there 
is white of egg. 

Test Avheat, rye, bran, flaxseed, corn, and other grains for protein. 
The kernels should be crushed or ground fine and heated for some 
time in the caustic potash solution before adding the copper sulphate 
solution. It sometimes takes several hours for the purple color, indi- 
cating the presence of protein, to appear. If it does not show during 
the class period, set aside and examine it at intervals for several 
hours. 

Exercise 20. — To Illustrate Tlant Fiber. 

Cotton is a good illustration of plant fiber. Flax is another. The 
fibrous bark of trees like the elm, hickory, and basswood are other 
good examples. 

[Bull. 105] 



19 

Pupils should be encouraged to make a collection of various 
kinds of plant fiber. 

Part 2.— The Soil. 

Soil 'is sometimes defined as the storehouse for plant food. It is 
derived mainly from rocks which have been broken down into fine 
particles by the action of water, air, heat, cold, and other natural 
agencies. It contains numerous substances which serve as plant food, 
and numerous minerals which are not considered essential to plant 
growth, but the composition of different soils varies as widely as the 
comi^osition of the rocks from which they came. It would be useless, 
therefore, to attempt to give the composition of an average soil. 
There is no such thing as an average soil. But there are many sub- 
stances which chemists have found in nearly all soils, and by taking 
the average of many chemical analyses we can get a pretty good no- 
tion of what we might expect to find in a fertile soil. X table of such 
averages is given below : 

Composition of soils. 

Per cent. 

Silica (largely sand) 80.00 

Oxid of iron (iron rust) 4.00 

Lime 1. 00 

Magnesia . 1. 00 

Acids (not including phcsphoric acid) .75 

Soda . 50 

rotasli . . 50 

Phosphoric acid . 15 

Nitrogen, in the form of nitrates, seldom exceeding .10 

Other matter sometimes found in plants, but not considered essential 

to plant growth 12.00 

Total 100. 00 

From this it will be seen that nearly all soil substances are plant 
foods and that the three essential fertilizers — nitrogen in the form of 
nitrates, phosphoric acid, and potash — constitute only a very small 
percentage of the soil. 

There are three classes of soluble compounds in the soil — acids, 
alkalis, and salts. The acids are characterized by their sour taste, 
and by other properties which will be discussed later. They have 
already been named. Lime, magnesia, soda, and- potash are the 
principal soil alkalis. The other soluble compounds are called salts. 
An alkali is a substance having power to combine with an acid, and 
the product of this combination is a salt. For example, potash is an 
alkali. If potash be added to a dilute solution of nitric acid, the 
salt known as saltpeter is formed. If the potash be added in the 
riglit amount to exactly neutralize the acid (see " Neutral soils,"' Ex- 
ercise 25), the saltpeter may be collected by the evaporation of the 

[Bull. 195] 



20 

solution to dryness in exactly the same manner as in the preparation 
of potash. Because it is formed from the union of potash and nitric 
acid chemists have given to saltpeter the chemical name of potassium 
nitrate. Plants will not grow well in a soil that has too great an ex- 
cess of either acid or alkali. 

Numerous and complex chemical changes, due to the liberation and 
recombination of acids and alkalis, are continually taking place in 
the soil. 

Exercise 21. — To Illustrate Plant Foods which must be Derived from 

THE Soil. 

Select from your collection of plant foods all those to be found in 
the soil (see Composition of Soils, above). You will observe that 
this collection includes the entire list wnth the exception of carbon 
and the oxygen and hydrogen to be found in w^ater. You wull re- 
member that these last three substances go to make up starch, sugar, 
oil, cellulose, and vegetable fiber. You will also note that the addi- 
tional substances required to make protein — i. e., nitrogen, sulphur, 
and phosphorus — are derived from the soil. 

Exercise 22. — To Illustrate Acids. 

Vinegar is an acid. It is sour. Add a few drops of sulphuric 
acid to a glass of water. Taste it. It, too, is sour. Add a few 
drops of nitric acid to a glass of w'ater. Taste it. It is sour. (Be 
very careful not to use much acid in these tests, as strong acids are 
very injurious.) The sour taste is an acid characteristic. 

Exercise 23. — To Illustrate Alkalis. 

Lime is an alkali. So, too, are magnesia, soda, ammonia, and pot- 
ash. Their chief characteristic is that they destroy the properties 
of an acid by combining with it. To illustrate this fill a glass half 
full of weak vinegar and sloAvly add to it limew^ater, about a tea- 
spoonful at a time, tasting the mixture after each addition of lime- 
water. The sour taste of the vinegar soon disappears — i. e., the solu- 
tion becomes neutral, or, if more limewater be added, alkaline. The 
same result wnll be obtained if soda, ammonia, or potash be added to 
the vinegar instead of lime^vater. 

Exercise 24. — To Test for Acids and Alkalis. 

Cochineal, a dyestuH' made from insects, may be purchased at any 
drug store. If a teaspoonful of cochineal be pulverized and dis- 
solved in a small bottle partly full of alcohol, it forms a colored 
liquid called by chemists an "indicator," from the fact that its color 

[Bull. 195] 



21 

depends on the character of the substance in which it is phiced. This 
cochineal indicator is reddish-brown in the presence of an acid, and 
purplish-bhie in the presence of an alkali. 

If a few drops of cochineal be added to weak vinegar or any other 
acid the liquid will assume a reddish-brown color. If the same in- 
dicator be added to any of the alkalis — limewater, ammonia, or the 
like — these liquids wnll assume a purplish-blue color. 

There is a kind of paper called litmus j)aper, wdiich is red in acids 
and blue in alkalis. If a slip of this paper be dipped in vinegar or 
any other acid it turns red. Now, if it be transferred to lye, am- 
monia, or any alkali, it immediately turns blue. 

These are the tests for acids and alkalis. Test lye, soapy water, 
cream of tartar, saleratus, baking pow^der, sour milk, lemon juice, or 
any fruit juice for acids and alkalis by the use of litmus paper or the 
cochineal indicator. 

Exercise 25. — To Test for Acidity and Alkalinity of Soils. 

Boil a sample of the soil to be tested in a small quantity of water, 
allow it to settle and, when perfectly clear, pour off the clear Avater 
into a white dish and test it with both blue and red litmus paper. 
If the soil was acid blue litmus paper will turn red; if it was alkaline 
red litmus paper will turn blue. Allow a little time, 5 or 10 minutes, 
if necessary, for the litnuis paper to change color. If litmus paper is 
not at hand test with cochineal. 

Neutral soils — that is, those which are neither acid nor alkaline — 
will have no effect upon the color of either indicator, the paper or the 
cochineal. 

Exercise 26. — To Show that Lime will " Sweeten " a Sour Soil. 

Take a can partly full of moist soil known to be acid. Test it to 
make sure. Stir into the soil a small handful of slaked lime and test 
as in Exercise 25. If it still shows acid repeat the addition of lime 
imtil the litmus or cochineal shows by the blue color that the soil is 
alkaline. 

Exercise 27. — To Show that Wood Ashes will " Sweeten " a Sour Soil. 

Secure an acid soil, test, and add to it w^ood ashes instead of lime, 
conducting this experiment exactly as in the preceding exercise. 
When the soil is "sweet" — that is, when the acid has been completely 
neutralized by the alkali — both litmus and cochineal will show blue 
color. 

[Bull. 195] 



22 

Exercise 28. — To Show that Irrigation with Unuerdrainage will Remove 

Alkali from the Soil. 

The alkali soils of the West are made fertile by running Avater on 
them from the top and drainino- it off from the bottom through tile 
drains. To show that this method removes alkali, prepare an alkali 
soil by mixing soda or potash with dry, sandy soil. Place this 
alkali soil in a tin can with holes in the bottom, through which the 
water may escape. Set this can in another dish, pour water on to the 
soil from the top, and test that which drains through by the use of 
litmus or cochineal. A blue color of the indicator produced by this 
drainage water shows that the alkali is being washed out of the soil. 

[Bull. 105] 



PJe'08 



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